ఇకపై ఒక నిమిషానికి 59 సెకండ్లే.. ఎందుకంటే..? | A day on Earth is now less than 24 hours why ?

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A day on Earth is now shorter than 24 hours.

Earth is rotating on its axis faster than it has in a half-century -- implying that each day on the planet is now shorter than 24 hours. Is this the first time that the planet is spinning faster or has it happened before.

Time is flying quicker this year as Earth is spinning around faster than it has in a half-century. This means each day on the blue planet is now shorter than 24 hours, owing to the increase in the speed of earth's rotation over the last 5 decades.

Making this startling revelation, scientists said that the earth's rotation is faster than normal due to which the length of a day is currently "ever-so-slightly" shorter than the normal 24 hours, Daily Mail reported.

2021 TO BE SHORTER THAN 2020?
The year 2020 included 28 shortest days since 1960 and 2021 is predicted to be even shorter.

According to Time and Date, on average, with respect to the Sun, Earth rotates once every 86,400 seconds, which equals 24 hours, or one mean solar day.

Scientists believe that an average day in 2021 will be milliseconds shorter than 86,400 seconds. Over the entire year, atomic clocks -- which have been keeping ultra-precise records of day length since the 1960s -- will have accumulated a lag of about 19 milliseconds, they said.

A report in the Live Science said, "The 28 fastest days on record (since 1960) all occurred in 2020, with Earth completing its revolutions around its axis milliseconds quicker than average."

According to atomic clocks, Earth has taken slightly less than 24 hours (86,400 seconds) to complete one rotation for the past 50 years.

According to the Daily Mail report, Earth recorded the shortest day (since records began) on July 19, 2020 -- when the day was milliseconds shorter than 24 hours.

Before 2020, the shortest day occurred in 2005. However, this record has been broken 28 times in the last 12 months.

HOW WE KNOW THAT EARTH IS SPEEDING UP
The International Earth Rotation and Reference Systems Service (IERS) officially measures the length of a day.

To determine the actual length of a day, scientists at the IERS "determine the exact speed of the Earth's rotation by measuring the precise moments a fixed star passes a certain location in the sky each day. This measurement is expressed as Universal Time (UT1), a type of solar time".

This UT1 is then compared to the International Atomic Time (TAI) -- a highly precise time scale that combines the output of some 200 atomic clocks maintained in laboratories around the world.

The length of a day is revealed by the deviation of UT1 from TAI over 24 hours.

A NEGATIVE LEAP?
According to reports, if the Earth's rotation gets out of sync with the "super-steady beat" of atomic clocks, a positive or negative leap second can be used to bring them back into alignment.

This has prompted scientists to call for the addition of a "negative leap second'.

WHAT IS A LEAP SECOND?
Leap seconds refer to adjustment of time, similar to leap years.

The National Institute of Standards and Technology (NIST) describes a leap second as a second that is added to Coordinated Universal Time (UTC) in order to keep it synchronized with astronomical time.

UTC is an atomic time scale, based on the performance of atomic clocks that are more stable than the Earth's rotational rate.

Astronomical time (UT1), or mean solar time, is based on the rotation of Earth, which is irregular.

HOW OFTEN A LEAP SECOND HAS BEEN ADDED OR SUBSTRACTED?
While the addition of a 'negative leap second' has never been done before, a total of 27 'leap seconds' have been added since the 1970s. This was done because Earth has taken slightly longer than 24 hours to complete a rotation over a decade. But since last year, the planet has been taking slightly less time, the report added.

Since 1972, scientists have added leap seconds about every year-and-a-half, on average, according to the National Institute of Standards and Technology (NIST).

The last addition came in 2016, when on New Year's Eve at 23 hours, 59 minutes and 59 seconds, an extra "leap second" was added.

According to the report, several scientists at the International Telecommunication Union suggested to let the gap between the astronomical and the atomic time widen until a "leap hour" is needed, which would minimize disruption to telecommunications.

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